1. Field of the Invention
The present invention relates to an ignition apparatus that is utilized mainly in an internal combustion engine.
2. Description of the Related Art
In recent years, the issues such as environment preservation and fuel depletion have been raised; measures for these issues are urgently required also in the automobile industry. The measures include, as an example, ultra-lean-combustion (referred to also as stratified-lean-combustion) operation of an internal combustion engine that utilizes a stratified air-fuel mixture. In the stratified lean combustion, the distribution of inflammable fuel-air mixtures may vary; therefore, an ignition apparatus capable of absorbing this variation is required.
A conventional ignition apparatus disclosed in Patent Document 1 is provided with an ignition plug that produces a spark discharge in a combustion chamber and a microwave generation apparatus that supplies energy to the spark discharge produced in the ignition plug. It is alleged that because the conventional ignition apparatus makes it possible to form larger discharge plasma, a great number of spatial igniting opportunities can be provided, the variation in the distribution of fuel-air mixtures can be absorbed, and the foregoing requirement on stratified lean combustion is satisfied.